William C. Schmidt

World-Wide Web survey research: Benefits, potential problems, and solutions

The World-Wide Web presents survey researchers with an unprecedented tool for the collection of data. The costs in terms of both time and money for publishing a survey on the Web are low compared with costs associated with conventional surveying methods. The data entry stage is eliminated for the survey administrator, and software can ensure that the data acquired from participants is free from common entry errors. Importantly, Web surveys can interactively provide participants with customized feedback. These features come at a price—ensuring that appropriately written software manages the data collection process. Although the potential for missing data, unacceptable responses, duplicate submissions, and Web abuse exist, one can take measures when creating the survey software to minimize the frequency and negative consequences of such incidents.

‘Inhibition of return’ without visual input

Inhibition of return (IOR) is the name that is associated with a response time (RT) delay to a visual stimulus presented at a recently cued spatial location. Two experiments with 26 undergraduates used an auditory analog to the visual IOR paradigm to examine whether manual RT inhibition would occur in the absence of visual input. In Experiment 1, subjects were instructed to prepare saccades, with their eyes closed, to the location of an auditory cue, and an RT delay to targets presented at the cued location was observed throughout the 1400 msec timecourse. Experiment 2 was used to examine the role of spatial distance between the auditory cue and the target, and found that as in the visual domain, there is a decrease in the magnitude of RT inhibition with increasing distance. Additionally, as in vision, support was found for the inhibition of targets presented in the same hemispace as the cue, whereas targets presented contralaterally were generally found to be facilitated. It was concluded that IOR is capable of acting in the auditory domain, and the possible neural origins of this effect are discussed. The result that IOR can occur even in the absence of visual input supports recent findings that perceptual representations of visual input are not the source of inhibition in this paradigm.

A decision-tree model of balance scale development

We present an alternative model of human cognitive development on the balance scale task. Study of this task has inspired a wide range of human and computational work. The task requires that children predict the outcome of placing a discrete number of weights at various distances on either side of a fulcrum. Our model, which features the symbolic learning algorithm C4.5 as a transition mechanism, exhibits regularities found in the human data including orderly stage progression, U-shaped development, and the torque difference effect. Unlike previous successful models of the task, the current model uses a single free parameter, is not restricted in the size of the balance scale that it can accommodate, and does not require the assumption of a highly structured output representation or a training environment biased towards weight or distance information. The model makes a number of predictions differing from those of previous computational efforts.

Inhibition of return is not detected using illusory line motion

Inhibition of return (IOR) is the name that has been assigned to a response time (RT) delay to a stimulus presented at a recently stimulated spatial location. A commonly held explanation for the origins of IOR is that perceptual processing is inhibited and that this inhibition translates into slower RT. Three experiments with 10 subjects were used to directly test this perceptual explanation. The first two experiments assessed the level of perceptual facilitation present in the IOR paradigm using the frequency and latency of illusory line motion judgments. Contrary to the predictions of the perceptual view, the line motion and RT measures revealed only speeded processing at previously stimulated spatial locations. Experiment 3 required a simple detection response and used the same stimulus and timing parameters as those in Experiments 1 and 2. IOR was present, replicating the recent finding that judgments based on perceptual qualities of the stimulus do not demonstrate a RT delay, whereas simple detection tasks do show RT inhibition at previously stimulated locations. These findings are discussed in relation to a number of hypotheses about the origin of the RT delay.

Disinhibition of return: Unnecessary and unlikely

Recently, from data obtained with a temporal order judgment (TOJ) task, Gibson and Egeth (1994) concluded that inhibition of return (IOR; a response time effect that reveals slower responding to targets at previously cued versus uncued locations) reflects impaired perceptual processing. By replotting their data, we demonstrate that the perception of temporal order is influenced only by the facilitatory effect of a cue at short stimulus onset asynchronies (SOAs) and is unaffected by IOR at long SO As. The target paper proposed that, when extra stimuli are presented at task-relevant locations (i.e., in the TOJ task), IOR is prevented by a hypothetical process that is known as disinhibition of return (DOR). We argue that the assumptions that IOR affects perceptual processing and that DOR exists are unnecessary, as a more parsimonious response-based interpretation of IOR is consistent with their data. Further, we summarize recent results and present new data that demonstrate that DOR is unlikely.

A Spatial Gradient of Acceleration and Temporal Extension Underlies Three Illusions of Motion

If an object (or cue), is presented and shortly afterwards a line is drawn with one end near to the object, motion away from the object location is induced within the line. This line-motion illusion has best been explained by postulating a facilitative spatial gradient that accelerates signal transmission most strongly near to the object, and less so with increasing distance away from the object. This simple accelerative-gradient model was tested in four experiments by either briefly presenting the line, or replacing the line rendering with a dot moving at high velocity towards (or away from) the initial object location. Observers first perceived motion away from the cue followed by motion towards the cue (hence this new illusion is referred to as the “two motion percepts”, or TMP illusion). The generality of the TMP illusion was investigated through the reports of forty-five inexperienced undergraduates who were presented with TMP displays. Observers who were asked to pictorially reproduce their motion experience, drew a line expanding away from the cue then contracting back towards it 85% of the time. Over 90% of individuals reported experiencing the illusion with a quickly moving dot. The effects of several presentation parameters were investigated by the moving-dot method, and it was concluded that the accelerative-gradient model by itself was inadequate to explain TMP phenomena. Two extended versions of the gradient model are proposed that place the locus of the TMP effects in properties of motion detection mechanisms or in temporal aspects of visual-signal transmission.

Operate your own World-Wide Web server

Although many researchers wishing to use the World-Wide Web for academic purposes rely on centralized Web services, they should be aware that it is neither expensive nor difficult to operate their own server. Doing so provides research-related benefits such as complete control over their host name and documents provided, the guaranteed ability to execute common gateway interface and server-side include programs, immediate access to their collected data, and the ability to better control who participates in their experiments. This paper surveys Web-server software features likely to be of interest to psychologists and conceptually summarizes their operation and use. The basic steps required to set up a Web server on popular microcomputers are reviewed, and security issues concerning Web-server operation are discussed. An accompanying resource Web page can assist users in setting up their own servers.

How does attention spread across objects oriented in depth

Previous evidence suggests that attention can operate on object-based representations. It is not known whether these representations encode depth information and whether object depth, if encoded, is in viewer- or objectcentered coordinates. To examine these questions, we employed a spatial cuing paradigm in which one corner of a 3-D object was exogenously cued with 75% validity. By rotating the object in depth, we can determine whether validity effects are modulated by 2-D or 3-D cue-target distance and whether validity effects depend on the position of the viewer relative to the object. When the image of a 3-D object was present (Experiments 1A and 1B), validity effects were not modulated by changes in 2-D cue-target distance, and shifting attention toward the viewer led to smaller validity effects than did shifting attention away from the viewer. When there was no object in the display (Experiments 2A and 2B), validity effects increased linearly as a function of 2-D cue-target distance. These results demonstrate that attention spreads across representations of perceived objects that encode depth information and that the object’s orientation in depth is encoded in viewer-centered coordinates.

Informational affordances: evidence of acquired perception–action sequences for information extraction

Visual objects can automatically prime actions allowing efficient interaction with them. The present study examined whether object perception can automatically prime actions leading to efficient information extraction. Participants in Experiment 1 learned to rotate a cube in a specific way with the end goal of efficiently revealing object-identifying information. In Experiments 2 and 3, the end goal of obtaining object-identifying information was removed, but the stimulus–response associations were preserved. Only object views associated with actions learned in the context of obtaining identifying information caused response interference and benefits in a subsequent test phase where the object was irrelevant. These results demonstrate the existence of informational affordances: perception–action sequences acquired with the goal of information extraction that are automatically primed during later exposure to the object. Perceptual priming of actions for efficient information extraction is an important component of expert performance and its use of action systems to optimally deal with the world.